The general hypothesis of this grant is that oxidative stress and the resulting increase in senescent cells in the trabecular meshwork contribute to the pathogenesis of this tissue in aging and primary open angle glaucoma. The specific hypothesis to be tested is that down-regulation of the microRNAs miR-155, mir-204 and mir-29 in response to chronic oxidative stress and cellular senescence lead to pathogenic changes in the outflow pathway by increasing cell contraction, extracellular matrix deposition, and chronic production of reactive oxygen species and inflammatory mediators in the cells of the trabecular meshwork. MiRNAs have been recently recognized as master regulators of gene networks and important cellular processes. Although a great deal of effort has been made in recent years to elucidate the biological functions of microRNAs in many tissues and their involvement in multiple pathologic conditions, the role of microRNAs in the pathogenesis of the trabecular meshwork in glaucoma has not been investigated. Therefore, the main objective of this proposal is to fill the current gap in knowledge regarding the role of microRNAs on the physiology and pathophysiology of the trabecular meshwork. The plan to test the hypothesis includes the following specific aims: 1) To test whether down-regulation of miR-155 in senescent tabecular meshwork cells contributes to a chronic production of ROS and inflammatory mediators, and increased cell contraction;2) To test whether down-regulation of miR-204 contributes to long-term survival of senescent cells and increased production of ROS and inflammatory mediators;and 3) To test whether miR-29 is an inhibitor the transforming growth factor beta 1 and Wnt pathways, and that downregulation of this miRNA by chronic oxidative stress leads to increased transforming growth factor beta1 expression and beta-catenin signaling, which contribute to increased ECM synthesis in human trabecular meshwork cells. The experimental design for these specific aims involves the identification of the main biological functions and mechanisms of action of miR-155, miR-204, and miR-29 in trabecular meshwork cells, as well as the evaluation of the effects in intraocular pressure induced by changes in expression of these microRNAs in living rats. The completion of these specific aims should provide new insights into the molecular mechanism involved in the regulation of key cellular functions relevant to the maintenance of normal levels of intraocular pressure in the eye and the pathogenesis of the trabecular meshwork in glaucoma. This information should be useful in identifying novel targets for therapeutic approaches aimed at delaying or preventing the abnormal elevation of intraocular pressure, which constitutes the best-characterized risk factor of developing glaucoma. PUBLIC HEALTH RELEVANCE: The completion of these specific aims should provide new insights into the molecular mechanism involved in the regulation of key cellular functions relevant to the maintenance of normal levels of intraocular pressure in the eye and the pathogenesis of the trabecular meshwork in glaucoma. This information should be useful in identifying novel targets for therapeutic approaches aimed at delaying or preventing the abnormal elevation of intraocular pressure, which constitutes the best-characterized risk factor of developing glaucoma.